This invention relates to hypodermic syringes and more particularly to hypodermic syringes for implanting solid objects beneath the skin of fish, birds, animals, and humans.
The art or science of restoring or preserving health has always included the injection or withdrawal of fluids from the bodies of living things. With the development of miniaturized mechanical and electrical devices that serve therapeutic purposes and more prosaic purposes such as tracking and identification, the implantation of solid things within a living body has become a reality. The implantation processes first utilized surgical procedures, but as miniaturization techniques became more and more effective, the surgical approach has given way to the use of devices modeled on the hypodermic syringe for injecting fluids.
The hypodermic syringe has long been used to aspirate or inject fluids for diagnostic or therapeutic purposes. It consists of a barrel which constitutes a fluid reservoir, a canula for insertion into the body, the canula being connected in a leak-proof way to the barrel, and a plunger that slides within the barrel and either pushes the fluid in the barrel through the canula and into the body or pulls fluid from the body into the barrel by means of an induced vacuum in the barrel.
The adaptation of the conventional hypodermic syringe for the implantation of solid objects in living bodies has taken a rather predictable path. The adaptation has focussed on objects that are elongated and usually cylindrical that will slide within a more-or-less conventional canula. A pusher rod that slides within the canula and pushes on the object during the implantation process is attached to the plunger, and the sliding seal between the plunger and the barrel is removed, thereby permitting air trapped in the barrel by the plunger to escape around the plunger.
This design has several deficiencies. First of all, the object to be implanted slides easily within the canula and can easily slide out the open end if the user points the syringe downward prior to making the implantation. Second, the "feel" of the syringe to the user during the implantation process is very different from the feel of the conventional fluid-injecting hypodermic syringe because of the absence of the fluid seal between barrel and plunger.
The present invention is intended to overcome both of these deficiencies.